Historical buildings have relatively low height, are usually massive and their
natural vibration period is rather low. Hence if such buildings are located in a
seismically active region, using base isolation systems is a very effective way for
improving their dynamic response. The idea of base isolation was known
hundreds years ago, however practical implementation of modern base isolators
started in the last few decades. The main advantage of a base isolation system is
that no elements should be added to an isolated building, which is especially
important for heritage architecture. A traditional base isolation system is
obtained by using two main base isolator types – elastomeric (neoprene) bearings
or friction pendulums. Hundreds of buildings all over the world are provided
with such isolators and have proved enhanced dynamic behaviour. Design of
base isolation systems and selection of their properties usually depend on
dynamic characteristics of the isolated building. The latter can be obtained by
non-destructive impulse testing of the structure before its protection. An
appropriate method for structural dynamic parameters experimental estimation
was developed by the authors. For this reason an impulse test was carried out on
a three-story structural part of a building designed for a seismic region. In some
cases the displacements at the base isolation level are rather big and exceed the
allowed limits. In such cases it is recommended to add dampers to the base
isolation system. Effective variable friction dampers were proposed and tested by
the authors. These dampers significantly reduce the displacements at the isolator
level (between the first floor column and foundation) and also yield further
improvement in the seismic response of a building.
Keywords: historic buildings, base isolation, impulse tests, variable friction
dampers, seismic response.